Process line control apparatus and method for controlling process line

ABSTRACT

A process line control apparatus which controls a process line including an annealing furnace ( 3 ) including a heating process apparatus executing a heating process and a cooling process apparatus executing a cooling process, the heating and cooling processes being continuously executed on a steel material, the apparatus having feed forward control means ( 112, 113 ) for measuring quality of the steel material by a material quality measuring apparatus ( 6 ) installed in an inlet stage ( 1 ) preceding the heating process in the annealing furnace ( 3 ), and on the basis of measurement results, determining modifications for respective temperature set values set by temperature setting means ( 111 ) for the heating and cooling apparatuses in the annealing furnace ( 3 ), and feedback control means ( 114, 115 ) for measuring the quality of the steel material by a material quality measuring apparatus ( 7 ) installed in an outlet stage ( 5 ) succeeding the cooling process in the annealing furnace ( 3 ), and on the basis of measurement results, determining modifications for the respective temperature set values set by the temperature setting means ( 111 ) for the heating and cooling apparatuses in the annealing furnace ( 3 ).

TECHNICAL FIELD

The present invention relates to an apparatus and method for controllinga process line such as a continuous annealing line or a plating line inwhich steel materials are continuously processed.

BACKGROUND ART

In general, in a line called a process line, annealing or plating isperformed on steel materials. The annealing is a process of heating acold-rolled and hardened steel material to about 700 to 900° C. forsoftening so that the steel material can be easily processed during apostprocess. In this case, the heating allows iron atoms to move easily,recovering and recrystallizing steel crystals hardened by theprocessing. New crystal grains of a size corresponding heating andtemperature maintenance conditions are generated and grown.

A conventional technique places a coil directly into a box-shapedfurnace for annealing (this is called batch annealing). However, inrecent years, a continuous annealing line (CAL) for continuous annealinghas often been used for treatment. This is because a CAL provides higherproductivity.

The quality of the above steel material includes strength and ductility,which are called mechanical properties. The mechanical properties aredetermined by a metallic structure such as a crystal grain size. Thus,determination of the metallic structure such as the crystal grain sizeenables the mechanical properties to be calculated.

However, the measurement of the crystal grain size requires steps ofcutting out, polishing, and microscopically observing specimens. Thisrequires much time and effort. Thus, the nondestructive measurement ofthe crystal grain size has been strongly desired. One method fornondestructively measuring the crystal grain size uses ultrasonicvibration.

For example, Patent Document 1 discloses a method for measuring thecrystal grain size or texture of a material on the basis of detectionvalues for a variation in the intensity of an ultrasonic wave appliedinto the material or for a speed at which the ultrasonic wavepropagates.

A recently developed laser ultrasonic apparatus or electromagneticultrasonic apparatus may be used to transmit and receive ultrasonicwaves. For example, Patent Document 2 discloses an example of the laserultrasonic apparatus. A measuring apparatus using electromagneticultrasonic waves needs to contact the steel material. However, the laserultrasonic apparatus is characterized by being able to set a longdistance between a surface of the material and a head of the apparatusand offers a particularly high utility value when hot measurements andonline measurements are required.

The material sensor is desirably of a non-contact and nondestructivetype in terms of durability or the like. It is possible to use not onlya sensor directly measuring the quality of a material such as magneticpermeability but also a sensor making indirect measurements by detectinga physical quantity such as electric resistance, an ultrasonicpropagation property, or a radiation scattering property which exhibitsa strong correlation with the material and converting the physicalproperty into a material quality such as the crystal grain size orformability. There are various such sensors, and Patent Document 3discloses an apparatus measuring the transformation quantity of a steelmaterial from a flux intensity detected by a flux detector.

Moreover, Patent Document 4 discloses a method for measuring an r value(Lankford value) utilizing electromagnetic ultrasonic waves. Here, the rvalue is the ratio of distortion in a plate width direction todistortion in a plate thickness direction which is observed when a steelmaterial is deformed by applying a tensile stress to the material. The rvalue is an index representing deep drawability. A larger r valueincreases a reduction in plate width more sharply than a reduction inplate thickness. This makes it possible to inhibit fracture and adecrease in strength during deep drawing, allowing the formability,particularly the deep drawability to be improved.

Proposed methods for nondestructively measuring the crystal grain sizeutilize Rayleigh scattering, the ultrasonic propagation speed, or thelike.

A CAL and a CGL may use the crystal grain size or r value of the steelmaterial measured after annealing in order to check whether or not adesired product quality has been obtained. In general, the crystal grainsize is desirably large and uniform and the r value is preferably large.Patent Document 5 shows a method for directly measuring these values tocontrol heating temperature.

Patent Document 1: Jpn. Pat. Appln. KOKAI Publication No. 57-57255

Patent Document 2: Jpn. Pat. Appln. KOKAI Publication No. 2001-255306

Patent Document 3: Jpn. Pat. Appln. KOKAI Publication No. 56-82443

Patent Document 4: Jpn. Pat. Appln. KOKOKU Publication No. 6-87054

Patent Document 5: Japanese Patent No. 2984869

DISCLOSURE OF INVENTION Problems to Be Solved by the Invention

However, the method shown in Patent Document 5 has the followingproblems.

Patent Document 5 illustrates a sensor utilizing laser ultrasonic wavesas a device measuring the grain size of ferrite described in ParagraphNo. 0014. However, a CAL and the like have achieved a maximum speed ofabout 1,000 m/min. It is difficult for the current techniques to measurethe crystal grain size of a steel material moving at such a high speed.High-frequency vibration may occur during high-speed movement, resultingin much noise.

Thus, an object of the present invention is to provide an apparatus andmethod for controlling a process line which can improve the quality of asteel material.

Means for Solving the Problems

To accomplish the object, an invention corresponding to claim 1 providesa process line control apparatus which controls a process linecomprising an annealing furnace which continuously executes heating andcooling processes on a steel material, the apparatus using a materialquality measuring apparatus to measure the quality of the steel materialat positions preceding the heating process and succeeding the coolingprocess in the annealing furnace and controlling the temperature of theannealing furnace on the basis of measurement results for the quality ofthe steel material.

To accomplish the object, an invention corresponding to claim 3 providesa process line control apparatus which controls a process linecomprising an annealing furnace which continuously executes heating andcooling processes on a steel material, the apparatus using a materialquality measuring apparatus to measure the quality of the steel materialat positions preceding the heating process and succeeding the coolingprocess in the annealing furnace as well as between positions succeedingthe heating process and preceding the cooling process in the annealingfurnace and controlling the temperature of the annealing furnace on thebasis of measurement results for the quality of the steel material.

To accomplish the object, an invention corresponding to claim 5 providesa process line control apparatus which controls a process linecomprising an annealing furnace which continuously executes heating andcooling processes on a steel material, the apparatus using a materialquality measuring apparatus to measure the quality of the steel materialat positions preceding the heating process and succeeding the coolingprocess in the annealing furnace and controlling a conveyance speed forthe steel material in the annealing furnace on the basis of measurementresults for the quality of the steel material.

To accomplish the object, an invention corresponding to claim 7 providesa process line control apparatus which controls a process linecomprising an annealing furnace which continuously executes heating andcooling processes on a steel material, the apparatus using a materialquality measuring apparatus to measure the quality of the steel materialat positions preceding the heating process and succeeding the coolingprocess in the annealing furnace as well as between positions succeedingthe heating process and preceding the cooling process in the annealingfurnace and controlling a conveyance speed for the steel material in theannealing furnace on the basis of measurement results for the quality ofthe steel material.

To accomplish the object, an invention corresponding to claim 9 providesa process line control apparatus which controls a process linecomprising an annealing furnace which continuously executes heating andcooling processes on a steel material, the apparatus using a materialquality measuring apparatus to measure the quality of the steel materialat positions preceding the heating process and succeeding the coolingprocess in the annealing furnace and controlling the temperature of theannealing furnace and a conveyance speed for the steel material in theannealing furnace on the basis of measurement results for the quality ofthe steel material.

To accomplish the object, an invention corresponding to claim 11provides a process line control apparatus which controls a process linecomprising an annealing furnace which continuously executes heating andcooling processes on a steel material, the apparatus using a materialquality measuring apparatus to measure the quality of the steel materialat positions preceding the heating process and succeeding the coolingprocess in the annealing furnace as well as between positions succeedingthe heating process and preceding the cooling process in the annealingfurnace and controlling the temperature of the annealing furnace and aconveyance speed for the steel material in the annealing furnace on thebasis of measurement results for the quality of the steel material.

To accomplish the object, an invention corresponding to claim 14provides a method for controlling a process line comprising an annealingfurnace which continuously executes heating and cooling processes on asteel material, the method being characterized by comprising a step ofusing a material quality measuring apparatus to measure the quality ofthe steel material at positions preceding the heating process andsucceeding the cooling process in the annealing furnace, checkingmeasurement results to determine whether or not the material isacceptable on the basis of determination criteria, and recording, in adatabase, those of the determinations which indicate the acceptabilityof the material, the determinations corresponding to processingconditions including set and/or actual values for heating and coolingtemperatures at the corresponding positions in the annealing furnaceand/or a set value for a conveyance speed for the steel material, and astep of reading the processing conditions recorded in the database andindicating the acceptability of the material to apply the processingconditions to the annealing furnace.

To accomplish the object, an invention corresponding to claim 15provides a method for controlling a process line comprising an annealingfurnace which continuously executes heating and cooling processes on asteel material, the method being characterized by comprising a step ofusing a material quality measuring apparatus to measure the quality ofthe steel material at positions preceding the heating process andsucceeding the cooling process in the annealing furnace as well asbetween positions succeeding the heating process and preceding thecooling process in the annealing furnace, checking measurement resultsto determine whether or not the material is acceptable on the basis ofdetermination criteria, and recording, in a database, those of thedeterminations which indicate the acceptability of the material, thedeterminations corresponding to processing conditions including setand/or actual values for heating and cooling temperatures at thecorresponding positions in the annealing furnace and/or a set value fora conveyance speed for the steel material, and a step of reading theprocessing conditions recorded in the database and indicating theacceptability of the material to apply the processing conditions to theannealing furnace.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a first embodiment of a processline control apparatus in accordance with the present invention.

FIG. 2 is a block diagram showing the configuration of a steel materialquality measuring apparatus in FIG. 2.

FIG. 3 is a block diagram showing the configuration of an ultrasonicsignal processing device in FIG. 2.

FIG. 4 is a block diagram showing the configuration of an embodiment ofa material quality model in FIG. 2.

FIG. 5 is a diagram showing an example of an ultrasonic pulse train.

FIG. 6 is a diagram showing an example of a schematic configuration of acontinuous annealing line (CAL) to which the present invention isapplied.

FIG. 7 is a block diagram illustrating a second embodiment of theprocess line control apparatus in accordance with the present invention.

FIG. 8 is a block diagram illustrating a third embodiment of the processline control apparatus in accordance with the present invention.

FIG. 9 is a block diagram illustrating a fourth embodiment of theprocess line control apparatus in accordance with the present invention.

FIG. 10 is a block diagram illustrating a first embodiment of a methodfor controlling a process line in accordance with the present invention.

FIG. 11 is a block diagram illustrating the first embodiment of themethod for controlling the process line in accordance with the presentinvention.

FIG. 12 is a diagram showing an example of a configuration of a databasefor use in the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below on the basis ofembodiments with reference to the drawings. The description below isintended for the continuous annealing line (CAL) shown in FIG. 6,described below. However, the present invention is similarly applicableto a CGL involving an annealing process and other stages involvingheating or cooling.

FIG. 1 is a block diagram illustrating a first embodiment in accordancewith the present invention. As described above, the CAL is composed ofroughly five stages, an inlet stage 1, an inlet looper 2, an annealingfurnace (hereinafter simply referred to as a furnace) 3, an outletlooper 4, and an outlet stage 5. The furnace 3 is composed of a heatingapparatus and a cooling apparatus, the heating apparatus being locatedupstream of the cooling apparatus. However, depending on a settemperature for each section in the furnace 3, the cooling apparatus maybe a temperature holding apparatus. For the set temperature for eachsection in the furnace 3, temperature setting means 111 for the heatingand cooling apparatuses preset, for example, temperature set values of800° C. for the heating apparatus and 300° C. for the cooling apparatus.

Material quality measuring apparatuses 6, 7 described below are arrangedin the inlet stage 1 and the outlet stage 5, respectively. Specifically,a crystal grain size and an r value are measured as the quality of asteel material before the material is carried into the furnace 3 andwhile the material is being carried out of the furnace 3.

A measurement result from the material quality measuring apparatuses 6is input to heating apparatus feed-forward (FF) control means 112. Onthe basis of the measurement result from the material quality measuringapparatus 6, the heating apparatus feed-forward (FF) control 112 meansdetermines that it is proper to set, for example, 830° C. for theheating apparatus in the furnace 3. The heating apparatus FF controlmeans 112 outputs +30° C. to the heating apparatus in the furnace 3.Further, a measurement result from the material quality measuringapparatuses 6 is input to cooling apparatus feed-forward (FF) controlmeans 113. On the basis of the measurement result from the materialquality measuring apparatus 6, the cooling apparatus feed-forward (FF)control means 113 determines that it is proper to set, for example, 290°C. for the cooling apparatus in the furnace 3. The cooling apparatus FFcontrol means 113 outputs −10° C. to the cooling apparatus in thefurnace 3.

A measurement result from the material quality measuring apparatuses 7is input to heating apparatus feed-forward (FF) control means 114. Onthe basis of the measurement result from the material quality measuringapparatus 7, the heating apparatus feed-forward (FF) control 114 meansdetermines that it is proper to set, for example, 810° C. for theheating apparatus in the furnace 3. The heating apparatus FF controlmeans 114 outputs +10° C. to the heating apparatus in the furnace 3.Further, a measurement result from the material quality measuringapparatuses 7 is input to cooling apparatus feed-forward (FF) controlmeans 115. On the basis of the measurement result from the materialquality measuring apparatus 7, the cooling apparatus feed-forward (FF)control means 115 determines that it is proper to set, for example, 295°C. for the cooling apparatus in the furnace 3. The cooling apparatus FFcontrol means 115 outputs −5° C. to the cooling apparatus in the furnace3. In the embodiment in FIG. 1, a conveyance speed for a steel materialin the furnace 3 is not varied but remains fixed.

With this configuration, in a process line comprising the furnace 3including the heating and cooling apparatuses continuously executingheating and cooling processes on a steel material, the material qualitymeasuring apparatuses 6, 7 measure the quality of the steel material atpositions preceding the heating process and succeeding the coolingprocess in the furnace 3. Then, on the basis of the measurement resultsfor the quality of the steel material, the heating and coolingapparatuses in the furnace are controlled. This enables the quality ofthe steel material to be improved.

Here, an example of the material quality measuring apparatuses 6, 7 willbe described with reference to FIGS. 2 to 5. In general, a laserultrasonic measuring apparatus is used to measure the crystal grainsize, and an electromagnetic ultrasonic measuring apparatus is used tomeasure the r value. However, the present invention is not limited tothis. Further, a plurality of different material quality measuringapparatuses may be arranged but are here collectively described as amaterial quality measuring apparatus. The material quality measuringapparatuses 6, 7 have substantially the same configuration. Accordingly,the material quality measuring apparatus 6 will be described below.

FIG. 2 is a block diagram showing the material quality measuringapparatus 6. For example, a YAG laser capable of a Q-switch operation isused as a pulse laser emitted by an ultrasonic oscillator 1. Here, theQ-switch operation makes a change from a low Q-value state to ahigh-Q-value state. For example, a Q-switch method controls theoscillation of a solid laser to obtain a high output pulse. Theprinciple of the Q-switch oscillation of the laser is such that theoptical loss of a laser resonator is initially increased to inhibit theoscillation to facilitate optical pumping and such that once the numberof excited atoms in a laser medium increases appropriately, the Q-valueof the resonator is rapidly increased to obtain a giant pulse.

Pulse laser light 61 a from the ultrasonic oscillator 61 has its beamdiameter reduced to an intended value by a lens (not shown). The pulselaser light 61 a is then applied to a surface of a measurement targetmaterial to be processed by a hot rolling mill, that is, a steelmaterial 62. An ultraviolet pulse 62 a generated at the surface of thesteel material 62 propagates through the steel material 62 tovibratorily displace a back surface of the steel material 62, whilerepeating multiple reflections by reciprocating through the steelmaterial 62. Thus, the vibratory displacement (ultrasonic detectionlaser light) 62 a′ at the back surface of the steel material 62 isdetected by an ultrasonic detector 63 using a continuous wave laser. Adetection signal 63 a is loaded into a digital waveform storage (notshown; for example, a digital oscilloscope) or the like and processed byan ultrasonic signal processing device 64 to obtain a waveformcharacteristic parameter identification result (multidimensionalfunction coefficient vector) 64 a.

The waveform characteristic parameter identification result 64 a isinput to a crystal grain size calculating device 65′, which thencalculates the crystal grain size. The calculated crystal grain size isinput to a crystal grain size correcting device 65, which corrects thecrystal grain size on the basis of the volume fraction of eachsubstructure from a material quality model 67 described below. A crystalgrain size output device 68 allows the corrected crystal grain size tobe, for example, audibly or visually perceived by users or to beexternally read.

Here, for example, a photorefractive interferometer is used as theultrasonic detector 63. The type of the interferometer is not limited tothe photorefractive interferometer but may be a Fabry-Perotinterferometer. Alternatively, a Michaelson interferometer may be usedprovided that the surface of the steel material is not rough.

Thus, with the ultrasonic vibration generated at the surface of thesteel material 62, since an optical path changes between reference lightand reflected light, the intensity of interference light changesaccording to the vibratory displacement of the surface of the steelmaterial 62.

Now, description will be given of the frequency property and reliabilityof the interferometer. That is, for a frequency range of about severaltens of MHz to 100 MHz, used to measure a grain size of 1 to 10 microns,the Fabry-Perot interferometer is more sensitive and advantageous thanthe photorefractive interferometer. However, experiments show that thephotorefractive interferometer poses no problem in a practical sense.

On the other hand, for reliability, the Fabry-Perot interferometerrequires a precise control mechanism because the interferometer mustsequentially operate two opposite mirrors so as to accurately maintainan appropriate gap between the mirrors. Consequently, the Fabry-Perotinterferometer is slightly unreliable in terms of the probability of adefect. In contrast, the photorefractive interferometer causes referencelight and reflection light to interfere with each other in the crystal.This results in the need for a reduced number of mechanical sections,enhancing the reliability in terms of the probability of a defect.

Now, a processing operation performed by an ultrasonic signal processingdevice 64 will be described with reference to a block diagram in FIG. 3.The ultrasonic detector 63 collects a plurality of compressional waveecho signals 63 a (S641). Then, the frequencies of the plurality ofcompressional wave echo signals are analyzed (S642). On the basis of adifference in spectral intensity among the multiple echo signals fromthe surface of the steel material 62, a decay curve for each frequencyis identified (calculated) (S643). Moreover, diffusion decay correctionsand transmission loss corrections are made as required to calculate thefrequency property of a decay constant. The frequency property of thedecay constant is fitted to a multidimensional function such as aquartic curve by a least square method (S644). This allows a coefficientvector 64 a for the multidimensional function to be determined.

A crystal grain size measured value do measured before corrections basedon the volume fraction of each substructure is calculated from thecoefficient vector of the multidimensional function obtained by fittingthe quartic curve to the decay constant and a scattering coefficient Sobtained from the steel material 62 for calibration.

As described above, the ultrasonic detector 63 measures ultrasonic pulsetrains including a first ultrasonic pulse, a second ultrasonic pulse, .. . . An example of the ultrasonic pulse train is shown in FIG. 5. Inthis case, energy contained in each ultrasonic pulse is graduallyreduced by a loss resulting from reflection or decay involved inpropagation through the material. When the first or second ultrasonicpulse is extracted and the frequency of the pulse is analyzed todetermine the energy of the pulse (power spectrum), the secondultrasonic pulse is propagated further than the first ultrasonic pulseby a distance corresponding to the double of the plate thickness t ofthe material. Consequently, proposed methods for nondestructivelymeasuring the crystal grain size include the use of Rayleigh scattering,the use of the propagation speed for ultrasonic waves, and the use of anultrasonic microscope.

Here, a typical method utilizing decay resulting from scattering(Rayleigh scattering) of the ultrasonic wave caused by crystal grains bymeans of will be shown.

The ultrasonic wave is classified into a longitudinal wave (P wave=bulkwave), a transverse wave (S wave), a surface wave (L wave=Rayleigh wave,Love wave), and a plate wave (SO mode, AO mode) according to thevibration form of the wave. The grain size measuring method utilizingRayleigh scattering uses the longitudinal wave (bulk wave).

The decay of the bulk wave is expressed by Equation 1 using a decayconstant a.

P=Po·exp(−a·x)  (1)

Here,

x: propagation distance in the steel material, andP, Po: sound pressure.

If the frequency of the bulk wave falls within a “Rayleigh region”, thedecay constant a is approximated by a quartic function of an ultrasonicfrequency f as shown in:

a=a1·f+a4·f ⁴  (2)

where f: bulk wave frequency, anda1, a4: coefficients.

(Here, the first item of Equation 2 is an absorptive decay item, and thesecond item is a Rayleigh scattering item)

The term “Rayleigh region” refers to a region in which the crystal grainsize is sufficiently small compared to the wavelength of the bulk wave,for example, a range expressed by Equation 3 (see Patent Document 5).

0.03<d/λ<0.3  (3)

Here,

d: crystal grain size, andλ: wavelength of the bulk wave.

Further, a quartic coefficient a4 in Equation 2 is known to beproportional to the third power of the crystal grain size d as shown in:

a4=S·d ³  (4)

where S: scattering constant.

The waveform of the bulk wave transmitted by a transmitter contains acertain distribution of frequency components. Consequently, analyzingthe frequency of the received waveform enables the decay rate of eachfrequency component to be obtained. Moreover, the propagation distancein the steel material is determined from a variation in the timerequired for transmission or reception. Thus, each of the coefficientsin Equation 2 can be determined on the basis of the propagation distanceand the decay rate of each frequency component. Moreover, the scatteringconstant S predetermined using standard samples allows the crystal grainsize d to be obtained on the basis of Equation 4.

The energy decays according to Equation 1. The amount of decay betweenthe first and second ultrasonic pulses is determined as a difference inpower spectrum between the first and second ultrasonic pulses. Thiscurve corresponds to the decay constant a in Equation 2 multiplied by adifference 2t in propagation distance. Thus, the coefficients ofEquation 2 for a unit propagation distance are determined by the leastsquare method or the like. Then, the scattering constant S predeterminedusing the standard sample and a4, one of the coefficients determined asdescribed above can be used to Equation 3 to determine the crystal grainsize measured value do measured before corrections with the volumefraction of each substructure. However, the present embodiment isdifferent from the conventional embodiments in that the presentembodiment has a subsequent step of predictively calculating thematerial quality on the basis of the material model 67 to makecorrections in accordance with the composition of each phase, that is,the volume fraction of each substructure.

As shown in FIG. 2, as is the case with the conventional technique, thematerial quality measuring apparatus based on ultrasonic vibrationmeasurements irradiates the measurement target material (steel material)62 with pulse laser light (excitation light) to measure the pulse ofultrasonic vibration excited by the steel material 62. Then, on thebasis of a change in the energy level of the measured pulse, thematerial quality measuring apparatus evaluates the steel material 62.

As shown in FIG. 2, a chemical component 661, a temperature andprocessing condition 662, a cooling condition 663, and the like areinput to a processing and thermal treatment condition input device 66 asinput values. The material quality predictive calculation is made on thebasis of the material quality model 67 to calculate the volume fractionof each substructure, for example, a pearlite rate. On the basis of thepearlite rate, the grain size calculated value is corrected. In general,the grain size measured value associated with ultrasonic vibration tendsto increases consistently with the pearlite rate. The correction is notlimited to those based on the material quality predictive calculationbut may be an input from a material quality sensor measuring thecomposition.

The material quality predictive calculation is executed, for example, asfollows. As shown in FIG. 4, the material quality model 67 is roughlycomposed of a hot processing model 671 and a transformation model 672.

The hot processing model 671 formulates dynamic recrystallizationoccurring during drafting performed by a roll and subsequent phenomenasuch as recovery, static recrystallization, and grain growth tocalculate the grain size (grain boundary area per unit volume) duringand after the rolling and a residual dislocation density, for example,an austenite state. The hot processing model 671 uses the austenitegrain size, temperature and inter-pass time information based ontemperature and speed, and equivalent strain and strain speedinformation based on a drafting pattern to make calculations (rollingaustenite grain size, dislocation density, and the like).

The temperature and inter-pass time information and the equivalentstrain and strain speed information are calculated on the basis ofrolling conditions (inlet plate thickness, outlet plate thickness,heating temperature, inter-pass time, roll diameter, and roll rotationnumber).

The transformation model 672 estimates the structural state aftertransformation such as the grain size and the fractions of pearlite andbainite for each generation and each growth.

The transformation model 672 uses temperature information based on acooling pattern in a runout table for the hot rolling machine (notshown) to output calculation results (ferrite grain size and thestructural fraction of each phase). The temperature information iscalculated on the basis of cooling conditions (air and water coolingsections, water amount density, plate passage speed in the coolingapparatus, and components) and the amount of transformation provided bythe transformation model. Instead of the above model, a precipitationmodel taking the effects of precipitated grains into account may beappropriately used if a trace amount of additional elements such as Nb,V, and Ti may be effective. Some metal materials such as aluminum andstainless are not transformed. Thus, no transformation model may be usedfor these materials.

The above calculations can be used to estimate (calculate) the volumefraction of each substructure (673). The resulting volume fractions areused in the equation shown below together with the grain size do,obtained by the ultrasonic vibration measurement.

d=do(1+k×R/100)  (5)

d: crystal grain size measured value (μm),do: crystal grain size measured value (μm) measured before correctionswith the volume fraction of each substructure,k: influence coefficient (a large number of samples are pre-measured andpre-identified) (−%), andR: substructure volume fraction (%).

As shown in the above equation, the grain size obtained by theultrasonic vibration measurement can be corrected to improve themeasuring accuracy of the ultrasonic vibration measurement. In thedescription below, the measured crystal grain size refers to the value dresulting from the correction based on Equation 5 or the uncorrectedvalue do. These values are collectively denoted by symbol D.

The above embodiment uses an optical fiber transmission path as atransmission path from a reception head to an interferometer and areception laser light source. This advantageously makes the receptionhead compact to increase the degree of freedom of the location anddirection of a measurement surface. Further, this advantageouslyrequires that only the small reception head be cooled even undermeasurement conditions in which the material is continuously exposed tohigh temperatures. The material quality measuring apparatuses 6, shownin FIGS. 2 to 4, described above, can accurately measure the crystalgrain size even if the steel material contains not only a ferritestructure but also a structure such as a pearlite or martensite. As aresult, the problem with Patent Document 5, described above, can besolved. Further, the steel material introduced into the CAL as a coldsteel material need not necessarily be limited to ferrite but may alsoinclude pearlite or beinite. The present embodiment is also applicableto the case in which the effects of the pearlite or beinite need to beremoved.

The heating apparatus FF control means 112 and the cooling apparatus FFcontrol means 113 control the set temperatures for the heating andcooling apparatuses or the conveyance speed for the steel material in afeed-forward (FF) manner on the basis of the measurement result from thematerial quality measuring apparatus 6. For example, it is assumed thatthe measurement result from the material quality measuring apparatus 6indicates an actual crystal grain size value Di and that the initial settemperature for the heating apparatus is calculated on the assumption ofa crystal grain size Do. A modification ΔTH for the set temperature forthe heating apparatus is expressed by:

$\begin{matrix}{{\Delta \; {TH}} = {\left( \frac{\partial T}{\partial D} \right)_{1}\left( {{Di} - {Do}} \right)}} & (6)\end{matrix}$

where (∂T/∂D)₁ is an influence coefficient indicating the effects of thecrystal grain size on the temperature and is generally determined in theform of the inverse of (∂D/∂T), that is, an influence coefficientindicating the effects of the temperature on the crystal grain size.

Although the influence coefficient is described as a linear variable,the coefficient may be obtained from a mathematical model and determinedusing a control method in accordance with the present inventiondescribed below.

The temperature for the cooling apparatus may be similarly modified. Themodification of the conveyance speed affects all the steel materials inthe furnace and is not always effective. However, the modification isapplicable if for example, the measurement result for the crystal grainsize obtained by the material quality measuring apparatus 6 indicate agradual and uniform variation. The speed may be changed taking intoaccount a heat balance to which the steel material is subjected when thetemperature is changed and a heat balance to which the steel material issubjected when the temperature is changed and a heat balance to whichthe steel material is subjected when the speed is changed.

The heating apparatus FB control means 114 and the cooling apparatus FBcontrol means 115 control the set temperatures for the heating andcooling apparatuses or the conveyance speed for the steel material in afeedback (FB) manner on the basis of the measurement result from thematerial quality measuring apparatus 7. For example, it is assumed thatthe measurement result from the material quality measuring apparatus 7indicates an actual crystal grain size value Do and that a targetcrystal grain size is defined as Daim. The modification ΔTH for the settemperature for the heating apparatus is expressed by:

$\begin{matrix}{{\Delta \; {TH}} = {\left( \frac{\partial T}{\partial D} \right)_{2}\left( {{Daim} - {Do}} \right)}} & (7)\end{matrix}$

where (∂T/∂D)₂ is an influence coefficient indicating the effects of thecrystal grain size on the temperature as is the case with Equation 6.

The heating apparatus FF control means 112 and the heating apparatus FBcontrol means 114 modify the set temperature preset for the heatingapparatus by the temperature and speed setting means 111 of the heatingand cooling apparatuses. The cooling apparatus FF control means 113 andthe cooling apparatus FB control means 115 modify the set temperaturepreset for the cooling apparatus by the temperature and speed settingmeans 111 of the heating and cooling apparatuses. Alternatively, theheating apparatus FF control means 112, the heating apparatus FB controlmeans 114, the cooling apparatus FF control means 113, and the coolingapparatus FB control means 115 modify the conveyance speed setting forthe steel material in the heating and cooling furnaces preset by thetemperature and speed setting means 111 of the heating and coolingapparatuses.

FIG. 6 shows an example of a schematic configuration of a CAL. The CALis composed of roughly five stages, the inlet stage 1, the inlet looper2, the annealing furnace (hereinafter simply referred to as the furnace)3, the outlet looper 4, and the outlet stage 5. The inlet stage 1comprises a payout reel 11 that pays out the steel material (coil), acutting machine 12 that cuts the steel material, a welding machine 13that joins the resulting pieces of the steel material together, a bridleroll 14, a washing apparatus 15 that washes the surface of the steelmaterial, and a bridle roll 16.

The steel material in the inlet stage 1 must be stopped while thewelding machine 13 is performing a welding operation. However, thein-furnace conveyance speed needs to be kept constant for appropriateannealing. Thus, the inlet looper 2 is an apparatus which stores thesteel material in order to maintain the in-furnace conveyance speed andwhich pays out the steel material at a constant speed. The inlet looper2 comprises an inlet looper main body 22.

The furnace 3 comprises a bridle roll 31, a heating section 32, asoaking section 33, a cooling section (1)34, and a cooling section(2)35. Each of the sections sets the temperature at a desired value tocontrol the temperature of the passing steel material.

Since the steel material may be stopped in the outlet stage 5 as is thecase with the inlet looper 1, the outlet looper 4 comprises an outletlooper main body 42 in order to keep the in-furnace conveyance speedconstant.

The outlet stage 5 comprises a bridle roll 51, a skin pass mill 52, atension leveler 73, a bridle roll 54, an end cutting machine 55, aninspection apparatus 56 including a plate thickness and width sensor, abridle roll 75, an oil attaching machine 58, a cutting machine 59, and awinding machine 50. The outlet stage may decelerate or stop so as toallow the inspection apparatus 56 to perform inspections or may stop soas to allow the end cutting machine 55 and the cutting machine 59 to cutthe steel material. This varies the steel material conveyance speed.

In a plating line (continuous galvanized line [CGL]), for example, ahot-dip plating line, an annealing process is usually executed before aplating process. The steel material is heated to obtain materialproperties similar to those obtained in the case of a CAL. The surfaceof the steel material is reduced by gas and activated so that thematerial can be easily plated. The configuration of a CGL oftencorresponds to the CAL in FIG. 6 in which a plating apparatus is addedto the outlet of the furnace 3.

Here, the specific installation range for the material quality measuringapparatus 6 is such that the material quality measuring apparatus 6 isinstalled in the inlet stage 1 at an appropriate position between therear end of the welding machine 13 and the rearmost end of the group ofthe bridle roll 14, washing apparatus 15, and bridle roll 16. Further,the specific installation range for the material quality measuringapparatus 7 is such that the material quality measuring apparatus 7 isinstalled in the outlet stage 5 at an appropriate position between thefront end of the bridle roll 51 and the rearmost end of the group of theskin pass mill 52, the tension leveler 53, the bridle roll 54, the endcutting machine 55, the inspection apparatus 56, the bridle roll 57, theoil attaching machine 58, and the cutting machine 59.

According to the first embodiment described above, the material qualitymeasuring apparatus 6 is installed in the inlet stage 1, and thematerial quality measuring apparatus 7 is installed in the outlet stage5. The material quality measuring apparatuses 6, 7 are used to measurethe crystal grain size or the r value. The quality of the steel materialcan thus be improved. This will be specifically described below. Theinlet stage 1 is installed in front of the heating process apparatus inthe annealing furnace 3, and the steel material is stopped in the inletstage 1. This is because the steel material needs to be stopped in theinlet stage 1 while the pieces of the steel material from the payoutreel 11 are welded together. Thus, even with the use of a laserultrasonic measuring apparatus measuring the crystal grain size, anexample of the material quality measuring apparatus 6, in a process linefor a steel material moving at, for example, 1,000 m/min., the stoppedsteel material prevents the adverse effect of much noise resulting fromhigh frequency vibration in the moving steel material. This enables thecrystal grain size of the steel material to be accurately measured.Further, even with the use of an electromagnetic ultrasonic measuringapparatus measuring the r value, an example of the material qualitymeasuring apparatus 6, the steel material stopped in the inlet stage 1is prevented from being damaged even when the r value for the steelmaterial is measured by contacting a contactor with the steel material.

Moreover, since the outlet stage 2 has the inspection apparatus 56, thesteel material is decelerated or stopped when the inspection apparatus56 performs inspections. Furthermore, since the outlet stage 2 has thecutting machine 59, the steel material is stopped so as to allow thecutting machine 59 to perform a cutting operation. Thus, as is the casewith the material quality measuring apparatus 6, even though a laserultrasonic measuring apparatus, an example of the material qualitymeasuring apparatus, is used as the material quality measuring apparatus7, installed in the outlet stage 2, the stopped steel material preventsthe adverse effect of much noise resulting from high frequency vibrationin the moving steel material. This enables the crystal grain size of thesteel material to be accurately measured. Further, even with the use ofan electromagnetic ultrasonic measuring apparatus measuring the r value,an example of the material quality measuring apparatus 6, the steelmaterial is prevented from being damaged even when the r value for thesteel material is measured by contacting the contactor with the steelmaterial.

Moreover, the first embodiment enables modeling on the basis of actualinformation on the material quality measured by the material qualitymeasuring apparatuses 6, 7 as well as actual information on the line.This allows a model suitable for the characteristics of the line to beconstructed and used for control. This in turn enables more precisecontrol, providing high-quality products. In connection with thedetermination of whether or not the material quality is acceptable, theneed for manual operations for downstream steps is eliminated.

FIG. 7 is a block diagram illustrating a second embodiment in accordancewith the present invention. FIG. 7 differs from FIG. 1 in that thesingle furnace 3 is divided into a furnace 3 a having a heatingapparatus and a furnace 3 b having a cooling apparatus, with a materialquality measuring apparatus 8 installed in the divided portion,specifically at an appropriate position between the soaking section 33and the cooling section (1)34, shown in FIG. 6, so as to allow thetemperatures of the heating and cooling apparatuses in the furnaces tobe controlled as follows. Specifically, the material quality measuringapparatus 8 measures the quality of the steel material. On the basis ofthe measurement results for the quality of the steel material,corrections are made of the temperatures of the heating apparatus(intermediate control means) 116 in the furnace 3 a and the coolingapparatus (intermediate control means) 117 in the furnace 3 b.

The second embodiment configured as described above exerts effectssimilar to those of the first embodiment, described above.

FIG. 8 is a block diagram illustrating a third embodiment in accordancewith the present invention.

Speed setting means 118 sets the conveyance speed for the steel materialin the furnace 3 at a set value of, for example, 10 m/s.

The material quality measuring apparatuses 6, 7 are arranged in theinlet stage 1 and outlet stage 5, respectively. Measurements are made ofthe quality of the steel material, specifically, the crystal grain sizeand r value of the steel material before the material is carried intothe furnace 3 and while the material is being carried out of the furnace3.

A measurement result from the material quality measuring apparatuses 6is input to heating apparatus feed-forward (FF) control means 122. Onthe basis of the measurement result from the material quality measuringapparatus 6, the heating apparatus feed-forward (FF) control 122 meansdetermines that it is proper to set the conveyance speed for the steelmaterial in the furnace 3 at, for example, 10.1 m/s. The heatingapparatus FF control means 122 outputs +0.1 m/s to a speed controlapparatus for the furnace 3. Further, a measurement result from thematerial quality measuring apparatuses 6 is input to cooling apparatusfeed-forward (FF) control means 123. On the basis of the measurementresult from the material quality measuring apparatus 6, the coolingapparatus feed-forward (FF) control means 123 determines that it isproper to set, for example, 9.9 m/s for the speed cooling apparatus forthe furnace 3. The cooling apparatus FF control means 113 outputs −0.1m/s to the speed control apparatus for the furnace 3.

A measurement result from the material quality measuring apparatuses 7is input to heating apparatus feed-forward (FF) control means 124. Onthe basis of the measurement result from the material quality measuringapparatus 7, the heating apparatus feed-forward (FF) control 124 meansdetermines that it is proper to set, for example, 10.2 m/s for the speedcontrol apparatus for the furnace 3. The heating apparatus FB controlmeans 124 outputs +0.2 m/s to a speed control apparatus for the furnace3. Further, a measurement result from the material quality measuringapparatuses 7 is input to cooling apparatus feedback (FB) control means125. On the basis of the measurement result from the material qualitymeasuring apparatus 7, the cooling apparatus feedback (FB) control means125 determines that it is proper to set, for example, 9.8 m/s for thespeed cooling apparatus for the furnace 3. The cooling apparatus FFcontrol means 125 outputs −0.2 m/s to the speed control apparatus forthe furnace 3. In the embodiment in FIG. 8, the temperatures for theheating and cooling apparatuses in the furnace 3 are not varied butremain fixed.

With this configuration, in the process line comprising the furnaceincluding the heating and cooling process apparatuses continuouslyexecuting heating and cooling processes, respectively, on the steelmaterial, the material quality measuring apparatus measures the qualityof the steel material at the positions preceding the heating process andsucceeding the cooling process in the furnace, and on the basis of themeasurement result for the quality of the steel material, the conveyancespeed for the steel material in the furnace is controlled. This enablesthe quality of the steel material to be improved.

FIG. 9 is a block diagram illustrating a fourth embodiment in accordancewith the present invention. FIG. 9 differs from FIG. 8 in that thematerial quality measuring apparatus 8 is installed between the soakingsection 33 of the furnace 3 a and the cooling section (1)34 of thefurnace 3 b, shown in FIG. 6, so that on the basis of measurement resultfrom the material quality measuring apparatus 8, the conveyance speed inthe furnaces 3 a and 3 b is controlled. Like the material qualitymeasuring apparatuses 6, 7, described above, the material qualitymeasuring apparatus 8 is a laser ultrasonic measuring apparatusmeasuring the crystal grain size and an electromagnetic ultrasonicmeasuring apparatus measuring the r value. The material qualitymeasuring apparatus 8 measures the quality of the steel materialslightly less accurately than the material quality measuring apparatuses6, 7.

On the basis of the measurement result from the material qualitymeasuring apparatus 8, the set temperature for the heating apparatus 3 ais controlled in a feedback (FB) manner. The concept of the controlmethod is similar to that shown in FIG. 1. When it is assumed that afterheating, the measurement result from the material quality measuringapparatus 8 indicates the actual crystal grain size value Do and thatthe target crystal diameter is defined as Daim, the modification ΔTH forthe set temperature for the heating apparatus can be determined in thesame manner as shown in Equation 7.

Cooling apparatus intermediate control means 127 controls the settemperature for the cooling apparatus in the feed-forward (FF) manner onthe basis of the measurement result from the material quality measuringapparatus 8. The control method is similar to that described above. Whenit is assumed that after heating, the measurement result from thematerial quality measuring apparatus 8 indicates the actual crystalgrain size value Di and that the initial set temperature for the heatingapparatus has been calculated on the assumption of the crystal grainsize Do, ΔTH can be determined in the same manner as shown in Equation6.

FIG. 10 is a block diagram illustrating a control method applied to acontrol apparatus corresponding to a combination of FIG. 1 (control ofthe temperature of the furnace 3) and FIG. 8 (control of the conveyancespeed for the steel material), described above, or a control apparatuscorresponding to a combination of FIG. 7 (control of the temperature ofthe furnace 3) and FIG. 9 (control of the conveyance speed for the steelmaterial), described above.

In FIG. 10, actual data such as the actual value of the set temperaturefor the heating apparatus in the furnace 3, the actual value of the settemperature for the cooling apparatus, and the actual value of theconveyance speed for the steel material is collected and recorded in adatabase 131. Further, if any sensor such as a plate thickness gauge, aplate width gauge, a steel material thermometer, or a tension gauge isplaced on the like, measured values from that sensor are also recordedin the database 131. The quality of the steel material is measured andrecorded in the database 131 before and after a heating process andafter a cooling process. Furthermore, information such as a platethickness target value and a plate width target value for the steelmaterial and the chemical components of the steel material is obtainedfrom an upper level computer 133 and recorded in the database 131. FIG.12 shows an example of the configuration of the database.

That is, the method for controlling the process line comprising thefurnace 3 which continuously executes heating and cooling processes onthe steel material comprises, as shown in FIGS. 1 and 8, a step of usingthe material quality measuring apparatuses 6, 7 to measure the qualityof the steel material at the positions preceding the heating process andsucceeding the cooling process in the furnace 3, checking themeasurement results to determine whether or not the material isacceptable on the basis of determination criteria, and recording, in thedatabase 131, those of the determinations which indicate theacceptability of the material, the determinations corresponding to theprocessing conditions including the set and/or actual values for theheating and cooling temperatures at the corresponding positions in thefurnace and/or the set value for the conveyance speed for the steelmaterial, and a step of reading the processing conditions recorded inthe database 131 and indicating the acceptability of the material toapply the processing conditions to the furnace 3.

The above control method is applicable not only to FIGS. 1 and 8 butalso to FIGS. 7 and 9. FIGS. 7 and 9 differ from FIGS. 1 and 8 in thatthe material quality measuring apparatuses 6, 7, and 8 measure thequality of the steel material at the positions preceding the heatingprocess and succeeding the cooling process in the furnace 3 as well asat the positions preceding the heating process and succeeding thecooling process in the furnace 3 between the heating and cooling processsections in the furnace 3.

Material quality acceptability determining means 132 determines whetheror not the steel material is acceptable on the basis of material qualitydata on the steel material obtained from the material quality measuringapparatus 7 or material quality data on the steel material checked forquality in a downstream step on the line, the data being included invarious pieces of information collected in the database 131. In FIG. 11,products ID I123456-01 and I123456-02 are the same in steel type(low-carbon [LC], ultra-low-carbon [UL] steel) and size but aredifferent in the temperatures at which the products were processed inthe heating and cooling apparatuses. In this case, I123456-02 obtained acrystal grain size and an r value which are closer to the respectivetarget values. Thus, the corresponding temperatures in the heating andcooling apparatuses are picked up as set value candidates for thesubsequent steel materials. Of course, such data needs to be collectedfor a large number of steel materials and statistically processed todetermine temperature settings and the like.

FIG. 11 is a block diagram illustrating a control method applied to acontrol apparatus corresponding to a combination of FIG. 1 (control ofthe temperature of the furnace 3) and FIG. 8 (control of the conveyancespeed for the steel material), described above, or a control apparatuscorresponding to a combination of FIG. 7 (control of the temperature ofthe furnace 3) and FIG. 9 (control of the conveyance speed for the steelmaterial), described above.

That is, the method for controlling the process line comprising thefurnace 3 which continuously executes heating and cooling processes onthe steel material comprises a step of using the material qualitymeasuring apparatuses 6, 7 to measure the quality of the steel materialat the positions preceding the heating process and succeeding thecooling process in the furnace 3, recording the measurement results forthe quality of the steel material in the database 131, and recording, inthe database 131, the set and actual values for the heating and coolingtemperatures at the appropriate positions in the furnace 3 and/or theset and actual values for the conveyance speed for the steel material aswell as information such as the plate thickness and width of the steelplate which is required to determine whether or not the material qualityis acceptable, a step of determining whether or not the material qualityis acceptable on the basis of the information recorded in the database131 and recording, in the database 131, those of the pieces ofinformation which have been determined to be acceptable, the informationindicating the temperature settings for the heating and coolingprocesses in the furnace and the conveyance speed for the steelmaterial, and a step of, for a steel material to be processed after thestep of recording the information in the database 131 is completed,applying, to the process line, processing conditions similar to thosefor the steel material determined to be acceptable which are recorded inthe database 131.

The above control method is applicable not only to FIGS. 1 and 8 butalso to FIGS. 7 and 9. FIGS. 7 and 9 differ from FIGS. 1 and 8 in thatthe material quality measuring apparatuses 6, 7, and 8 measure thequality of the steel material at the positions preceding the heatingprocess and succeeding the cooling process in the furnace 3 as well asat the positions preceding the heating process and succeeding thecooling process in the furnace 3 between the heating and cooling processsections in the furnace 3.

As described above, the processing conditions for the steel materialdetermined to be qualitatively acceptable are recorded in the database131. This enables the processing conditions for the steel material to beread and reflected in the settings for the furnace 3 for the subsequentsteel materials. In this case, when the processing conditions for thesteel materiel determined to be acceptable are read, it may be necessaryto execute, for example, a process of averaging a plurality ofprocessing conditions.

The following method is an example of determination of the influencecoefficient for the effect of the temperature on the crystal grain size,described in Equation 1.

When it is assumed that the furnace has n sections for the heating andcooling apparatuses, heat input to the steel material and determinedfrom the actual temperature values and conveyance speeds obtained fromthe respective sections is defined as Qi (i=1 to n). The crystal grainsize measured by the material quality measuring apparatus 6 is definedas Di, and the crystal grain size measured by the material qualitymeasuring apparatus 7 is defined as Do. Then, a regression equation isdefined by Equation 8.

Do=a(0)+a(1)Q(1)+a(2)Q(2)+ . . . +a(n)Q(n)+a(n+1)Di  (8)

Here, Q(i) (i=1-n) denotes, when it is assumed that the furnace has nsections for the heating and cooling apparatuses, the heat input to thesteel material and determined from the actual temperature values andconveyance speeds obtained from the respective sections. Di denotes thecrystal grain size measured by the material quality measuring apparatus6. Do denotes the crystal grain size measured by the material qualitymeasuring apparatus 7. a(0), a(1), . . . , a(n), a(n+1) denotes aninfluence coefficient for the effect of the heat quantity on the outletcrystal grain size in each section of the heating furnace.

By determining each of the coefficients of Equation 8 on the basis ofthe data stored in the database 131, it is possible to determine theinfluence coefficient for the effect of the heat quantity on the outletcrystal grain size in each section. The conversion of the heat quantityinto the temperature and speed can be based on a common idea. This isapplicable not only to the crystal grain size but also to the r value.Further, the multiple regression equation need not be used but, forexample, a neural network may be used. With the neural network, an inputlayer is defined as the input heat, the crystal grain size Di, or thelike, and an output layer is defined as Do. The neural network may beallowed to learn a measured Do as a teaching signal.

Furthermore, the relationship between the crystal grain size or r valueand the annealing temperature for the steel material is partiallymodeled using equations. However, actual annealing stages are very longand must thus be treated as distributed parameter systems. Thus, thetemperature setting cannot be easily calculated using the equations.

Thus, the material quality measuring apparatuses 6, 7, and/or 6, 7, 8measure the quality of the steel material and record the results in thedatabase 131. Further, the actual values for the heating and coolingtemperatures at the appropriate positions in the furnace 3, the actualvalue for the conveyance speed for the steel material, and the requiredinformation such as the plate thickness, plate width, and chemicalcomponents of the steel material are also recorded in the database 131.Moreover, a determination is made of whether or not the desired materialquality has been obtained at the temperature settings for the heatingand cooling apparatuses and the conveyance speed for the steel material.The determination is also recorded in the database 131. A heatingprocess, a cooling process, and a conveyance speed meeting conditionssimilar to those determined to be acceptable are retrieved from thedatabase 131 and applied to the steel materials to be subsequentlyprocessed. This enables the appropriate steel material quality to beobtained.

Further, a model for the quality of the steel material, the temperaturesettings for the heating and cooling apparatuses, and the conveyancespeed for the steel material is automatically generated from theinformation recorded in the database 131 and used for control.

(Variation)

In the above description, the material quality measuring apparatus inFIG. 2, described above, comprises the processing and thermal treatmentcondition input device 66 and the material quality model setting device67. However, the processing and thermal treatment condition input device66 and the material quality model setting device 67 may be omitted fromthe material quality measuring apparatuses 6, 7, 8 applied to thepresent invention. The material quality measuring apparatuses 6, 7, 8applied to the present invention have only to be able to measure thecrystal grain size and the r value.

EFFECTS OF THE INVENTION

The present invention makes it possible to provide an apparatus andmethod for controlling a process line, which can improve the quality ofthe steel material.

INDUSTRIAL APPLICABILITY

The present invention is applicable not only to a continuous annealingline but also to a plating line involving an annealing process and otherstages involving a heating or cooling process.

1. A process line control apparatus which controls a process linecomprising an annealing furnace which continuously executes a heatingprocess and a cooling process on a steel material, the apparatuscharacterized by: measuring, by a material quality measuring apparatus,quality of the steel material at a position preceding the heatingprocess and a position succeeding the cooling process in the annealingfurnace and controlling the temperature of the annealing furnace on thebasis of measurement results for the quality of the steel material.
 2. Aprocess line control apparatus which controls a process line comprisingan annealing furnace including a heating process apparatus and a coolingprocess apparatus which continuously execute a heating process and acooling process, respectively, on a steel material, the process linecontrol apparatus characterized by: measuring, by a material qualitymeasuring apparatus, quality of the steel material at a positionpreceding the heating process apparatus in the annealing furnace andsetting temperatures for the heating and cooling apparatuses in theannealing furnace on the basis of measurement results for the quality ofthe steel material yet to be subjected to the heating process, andmeasuring, by a material quality measuring apparatus, the quality of thesteel material at a position succeeding the cooling process apparatus inthe annealing furnace and correcting the temperatures for the heatingand cooling apparatuses in the annealing furnace on the basis of themeasurement results for the quality of the steel material.
 3. A processline control apparatus which controls a process line comprising anannealing furnace which continuously executes a heating process and acooling process on a steel material, the apparatus characterized by:measuring, by a material quality measuring apparatus, quality of thesteel material at a position preceding the heating process and aposition succeeding the cooling process in the annealing furnace as wellas between a position succeeding the heating process and a positionpreceding the cooling process in the annealing furnace and controllingthe temperature of the annealing furnace on the basis of measurementresults for the quality of the steel material.
 4. A process line controlapparatus which controls a process line comprising an annealing furnaceincluding a heating process apparatus and a cooling process apparatuswhich continuously execute a heating process and a cooling process,respectively, on a steel material, the process line control apparatuscharacterized by: measuring, by a material quality measuring apparatus,quality of the steel material at a position preceding the heatingprocess apparatus in the annealing furnace in order to measure thequality of the steel material yet to be subjected to the heating processand measuring, by a material quality measuring apparatus, the quality ofthe steel material between a position succeeding the heating process anda position preceding the cooling process in the annealing furnace andsetting temperatures for the heating and cooling apparatuses in theannealing furnace on the basis of measurement results for the quality ofthe steel material, and measuring, by a material quality measuringapparatus, the quality of the steel material at a position succeedingthe cooling process apparatus in the annealing furnace and correctingthe temperatures for the heating and cooling apparatuses in theannealing furnace on the basis of the measurement results for thequality of the steel material.
 5. A process line control apparatus whichcontrols a process line comprising an annealing furnace whichcontinuously executes a heating process and a cooling process on a steelmaterial, the apparatus characterized by: measuring, by a materialquality measuring apparatus, quality of the steel material at a positionpreceding the heating process and a position succeeding the coolingprocess in the annealing furnace and controlling a conveyance speed forthe steel material in the annealing furnace on the basis of measurementresults for the quality of the steel material.
 6. A process line controlapparatus which controls a process line comprising an annealing furnaceincluding a heating process apparatus and a cooling process apparatuswhich continuously execute a heating process and a cooling process,respectively, on a steel material, the process line control apparatuscharacterized by: measuring, by a material quality measuring apparatus,quality of the steel material at a position preceding the heatingprocess apparatus in the annealing furnace and setting a conveyancespeed for the steel material in the annealing furnace on the basis ofmeasurement results for the quality of the steel material yet to besubjected to the heating process, and measuring, by a material qualitymeasuring apparatus, the quality of the steel material at a positionsucceeding the cooling process apparatus in the annealing furnace andcorrecting the conveyance speed for the steel material in the annealingfurnace on the basis of the measurement results for the quality of thesteel material.
 7. A process line control apparatus which controls aprocess line comprising an annealing furnace which continuously executesa heating process and a cooling process on a steel material, theapparatus characterized by: measuring, by a material quality measuringapparatus, quality of the steel material at a position preceding theheating process and a position succeeding the cooling process in theannealing furnace as well as between a position succeeding the heatingprocess and a position preceding the cooling process in the annealingfurnace and controlling a conveyance speed for the steel material in theannealing furnace on the basis of measurement results for the quality ofthe steel material.
 8. A process line control apparatus which controls aprocess line comprising an annealing furnace including a heating processapparatus and a cooling process apparatus which continuously execute aheating process and a cooling process, respectively, on a steelmaterial, the process line control apparatus characterized by:measuring, by a material quality measuring apparatus, quality of thesteel material at a position preceding the heating process apparatus inthe annealing furnace in order to measure the quality of the steelmaterial yet to be subjected to the heating process and measuring, by amaterial quality measuring apparatus, the material quality measuringapparatus to measure the quality of the steel material between aposition succeeding the heating process and a position preceding thecooling process in the annealing furnace and setting a conveyance speedfor the steel material in the annealing furnace on the basis ofmeasurement results for the quality of the steel material, andmeasuring, by a material quality measuring apparatus, the quality of thesteel material at a position succeeding the cooling process apparatus inthe annealing furnace and correcting the conveyance speed for the steelmaterial in the annealing furnace on the basis of the measurementresults for the quality of the steel material.
 9. A process line controlapparatus which controls a process line comprising an annealing furnacewhich continuously executes a heating process and a cooling process on asteel material, the apparatus characterized by: measuring, by a materialquality measuring apparatus, quality of the steel material at a positionpreceding the heating process and a position succeeding the coolingprocess in the annealing furnace and controlling the temperature of theannealing furnace and a conveyance speed for the steel material in theannealing furnace on the basis of measurement results for the quality ofthe steel material.
 10. A process line control apparatus which controlsa process line comprising an annealing furnace including a heatingprocess apparatus and a cooling process apparatus which continuouslyexecute a heating process and a cooling process, respectively, on asteel material, the process line control apparatus characterized by:measuring, by a material quality measuring apparatus, quality of thesteel material at a position preceding the heating process apparatus inthe annealing furnace and setting temperatures for the heating andcooling apparatuses in the annealing furnace and a conveyance speed forthe steel material in the annealing furnace on the basis of measurementresults for the quality of the steel material yet to be subjected to theheating process, and measuring, by a material quality measuringapparatus, the quality of the steel material at a position succeedingthe cooling process apparatus in the annealing furnace and correctingthe temperatures for the heating and cooling apparatuses in theannealing furnace and the conveyance speed for the steel material in theannealing furnace on the basis of the measurement results for thequality of the steel material.
 11. A process line control apparatuswhich controls a process line comprising an annealing furnace whichcontinuously executes a heating process and a cooling process on a steelmaterial, the apparatus characterized by: measuring, by a materialquality measuring apparatus, quality of the steel material at a positionpreceding the heating process and a position succeeding the coolingprocess in the annealing furnace as well as between a positionsucceeding the heating process and a position preceding the coolingprocess in the annealing furnace and controlling the temperature of theannealing furnace and a conveyance speed for the steel material in theannealing furnace on the basis of measurement results for the quality ofthe steel material.
 12. A process line control apparatus which controlsa process line comprising an annealing furnace including a heatingprocess apparatus and a cooling process apparatus which continuouslyexecute a heating process and a cooling process, respectively, on asteel material, the process line control apparatus characterized by:measuring, by a material quality measuring apparatus, quality of thesteel material at a position preceding the heating process apparatus inthe annealing furnace in order to measure the quality of the steelmaterial yet to be subjected to the heating process and measuring, by amaterial quality measuring apparatus, the quality of the steel materialbetween a position succeeding the heating process and a positionpreceding the cooling process in the annealing furnace and settingtemperatures for the heating and cooling apparatuses in the annealingfurnace and a conveyance speed for the steel material in the annealingfurnace on the basis of measurement results for the quality of the steelmaterial, and measuring, by a material quality measuring apparatus, thequality of the steel material at a position succeeding the coolingprocess apparatus in the annealing furnace and correcting thetemperatures for the heating and cooling apparatuses in the annealingfurnace and the conveyance speed for the steel material in the annealingfurnace on the basis of the measurement results for the quality of thesteel material.
 13. The process line control apparatus according to anyof claims 1 to 12, characterized in that the measurement of the qualityof the steel material by the material quality measuring apparatus isperformed after the conveyance of the steel material has been stopped orafter the conveyance speed for the steel material has decreased from anormal conveyance speed.
 14. A method of controlling a process linecomprising an annealing furnace which continuously executes a heatingprocess and a cooling process on a steel material, the methodcharacterized by comprising: a step of measuring, by a material qualitymeasuring apparatus, quality of the steel material at a positionpreceding the heating process and a position succeeding the coolingprocess in the annealing furnace, checking measurement results todetermine whether or not the material is acceptable on the basis ofdetermination criteria, and recording, in a database, those of thedeterminations which indicate the acceptability of the material, thedeterminations corresponding to processing conditions including setand/or actual values for a heating temperature and a cooling temperatureat the corresponding positions in the annealing furnace and/or a setvalue for a conveyance speed for the steel material; and a step ofreading the processing conditions recorded in the database andindicating the acceptability of the material to apply the processingconditions to the annealing furnace.
 15. A method of controlling aprocess line comprising an annealing furnace which continuously executesa heating process and a cooling process on a steel material, the methodcharacterized by comprising: a step of measuring, by a material qualitymeasuring apparatus, quality of the steel material at a positionpreceding the heating process and a position succeeding the coolingprocess in the annealing furnace as well as between a positionsucceeding the heating process and a position preceding the coolingprocess in the annealing furnace, checking measurement results todetermine whether or not the material is acceptable on the basis ofdetermination criteria, and recording, in a database, those of thedeterminations which indicate the acceptability of the material, thedeterminations corresponding to processing conditions including setand/or actual values for a heating temperature and a cooling temperatureat the corresponding positions in the annealing furnace and/or a setvalue for a conveyance speed for the steel material; and a step ofreading the processing conditions recorded in the database andindicating the acceptability of the material to apply the processingconditions to the annealing furnace.
 16. A method of controlling aprocess line comprising an annealing furnace including a heating processapparatus and a cooling process apparatus which continuously execute aheating process and a cooling process, respectively, on a steelmaterial, the method characterized by comprising: a step of measuring,by a material quality measuring apparatus, quality of the steel materialat a position preceding the heating process and a position succeedingthe cooling process in the annealing furnace, recording the measurementresults for the quality of the steel material in a database, andrecording, in the database, set and actual values for a heatingtemperature and a cooling temperature at appropriate positions in theannealing furnace and/or a set and an actual value for a conveyancespeed for the steel material as well as information such as the platethickness and width of the steel plate which is required to determinewhether or not the material quality is acceptable; a step of determiningwhether or not the material quality is acceptable on the basis of theinformation recorded in the database and recording, in the database,those of the pieces of information which have been determined to beacceptable, the information indicating the temperature settings for theheating and cooling processes in the furnace and the conveyance speedfor the steel material; and a step of, for a steel material to beprocessed after the step of recording the information in the database iscompleted, applying, to the process line, processing conditions similarto those for the steel material determined to be acceptable which arerecorded in the database.
 17. A method of controlling a process linecomprising an annealing furnace including a heating process apparatusand a cooling process apparatus which continuously execute a heatingprocess and a cooling process, respectively, on a steel material, themethod characterized by comprising: a step of measuring, by a materialquality measuring apparatus, quality of the steel material at a positionpreceding the heating process and a position succeeding the coolingprocess in the annealing furnace as well as at a position between theheating and cooling apparatuses in the annealing furnace, recording themeasurement results for the quality of the steel material in a database,and recording, in the database, set and actual values for a heatingtemperature and a cooling temperature at appropriate positions in theannealing furnace and/or a set and an actual value for a conveyancespeed for the steel material as well as information such as the platethickness and width of the steel plate which is required to determinewhether or not the material quality is acceptable; a step of determiningwhether or not the material quality is acceptable on the basis of theinformation recorded in the database and recording, in the database,those of the pieces of information which have been determined to beacceptable, the information indicating the temperature settings for theheating and cooling processes in the furnace and the conveyance speedfor the steel material; and a step of, for a steel material to beprocessed after the step of recording the information in the database iscompleted, applying, to the process line, processing conditions similarto those for the steel material determined to be acceptable which arerecorded in the database.